Removing overlapping faces and internal edges from a 2d geometry
If you are on 2.79, you could use the TinyCAD addon:


Make sure that all your planes are on the same level on the Z axis, if not select all and press SZ0.
Keep everything selected and press W > TinyCAD > XALL
Only the edges remain, press W > Remove Doubles.
Delete the useless vertices with X > Vertices.
Fill the faces with F.
If you want to keep a central hole you need to have enough topology.